1. Field of the Invention
The present invention pertains to the field of flying toy aircraft and more particularly is directed to improvements in captive, line controlled electrically powered aircraft of the type which are supplied with electric power through the flight control lines.
2. State of the Prior Art
Electrically powered model aircraft were known at least as early as 1921 as evidenced by U.S. Pat. No. 1,364,203 issued to Modlin, which shows a model aircraft suspended from an electric fixture and provided with an electric motor supplied with electric power through the supporting wires. As electric motors evolved into smaller and more efficient units, it became possible to construct model aircraft capable of generating sufficient lift for true aerodynamic flight provided that power was supplied from a ground-based power source, such as a battery. Examples of such toy aircraft are disclosed in U.S. Pat. No. 2,439,054 issued to Mosthof and U.S. Pat. No. 3,579,905 issued to Radford et al. Further technological progress has made possible model aircraft capable of carrying their own power supply in the form of a rechargeable electric storage cell of capacity sufficient to power the aircraft during relatively brief flights. These aircraft require frequent recharging of the internal battery, usually after each flight and generally have not proven to be very popular.
Line controlled aircraft powered by gasoline engines have been long known as exemplified by U.S. Pat. No. 2,292,416 to Walker issued in 1941, and later U.S. Pat. Nos. 2,743,068 to Walker and 3,110,126 to Kretzmer, Jr. Gasoline powered captive flight aircraft have proven popular, particularly with novice hobbyists, but require the cooperation of two individuals for launching into the air; the "pilot" i.e. person who is to control the aircraft, must stand away from the aircraft with the control lines more or less taut, while an assistant starts the engine and holds back the aircraft until given the signal to let it roll towards take off. The small engines typically used do not have self-starters and the propellers must be manually turned to start the engine. Furthermore, once started, no means are usually provided for stopping the engine before it runs out of fuel. Therefore, once the aircraft has taken off, the operator is committed to a flight lasting for as long as the fuel supply allows. The small gasoline engines are quite noisy since typically no mufflers are provided, and are messy to work with because of inevitable spillage of fuel and lubricant fluids. Moreover, unless handled carefully, these engines are capable of inflicting serious bodily injury, particularly during engine start up when the propeller must be manually turned over until the engine fires, which frequently occurs in an unpredictable manner.
Both the Mosthof and Radford et al., patents teach the idea of supplying electric power to the model aircraft through the same pair of wires used to control an aerodynamic control surface, namely the tail elevator of the aircraft. In Mosthof, the two control/power wires run directly to the elevator through curved guide conduits in the fuselage, and a pair of slack wires are connected between a point along the control wires and the electric motor for supplying power to the latter. In flight, the wires connected to the elevator are held taut by centrifugal force as the aircraft flies in circles about the operator on the ground who is then able to adjust the flight attitude of the aircraft by pulling alternately on one or the other control wire to thereby raise or lower the elevator surface. Radford et al., improves over the Mosthof system by providing a bell crank pivotably mounted to the air frame. The control wires are connected to opposite ends of the bellcrank cross-arm while a short arm on the bell crank is mechanically connected through a control rod to the hinged elevator. Slack conductive wires in turn are connected for carrying electric current from the control line ends on the cross arm to the propeller motor.
A continuing source of difficulty encountered in arrangements such as in Radford and also in Mosthof, is the susceptibility of the current carrying control lines to break under the strain of continuous centrifugal force and repeated flexing, particularly at the connections to the aircraft and the control handle. A direct mechanical or welded joint between the conductor wire and the bell crank as in Radford has been found to break after a relatively short flying time because of the aforementioned simultaneous centrifugal loading and flexing strain. The same problem occurs at the connection with the control handle held by the operator on the ground. As the aircraft circles the operator, the control handle tends to either lead or lag the aircraft in its circular path consequently subjecting the wires to repeated flexing at the ground end as well.
A continuing need therefore exists for improvement in model aircraft of the Radford type, particularly a need for dependable mechanical and electrical connections throughout the system capable of performing reliably under repeated mechanical flexing and loading.